This invention relates to a sheet finisher which receives sheets having an image formed on them in an image forming apparatus such as an electro-photographic copying machine, a printer, a facsimile apparatus, and a printing machine, and ejects them on to an output tray after applying a binding process by a binding means, to an image forming apparatus equipped with a sheet finisher, and to a sheet conveyance apparatus.
A sheet finisher which collates a plurality of sheets having an image formed on them ejected from an image forming apparatus and applies finish-processing by an finish-processing means such as a binding means are utilized.
The sheet finisher of this kind is functionally connected to an image forming apparatus such as a copying machine, a printer, and a facsimile apparatus, and is driven in accordance with the sequential operation of the copying or printing process.
Accordingly, for an image forming apparatus being capable of processing the image forming process at a high speed, it is required a sheet finisher being capable of high-speed processing which can perform the function in accordance with the process speed.
With respect to such a sheet finisher being capable of high-speed processing, it has already been disclosed in Tokkaisho 60-142359, Tokkaisho 60-158463, Tokkaisho 62-39169, Tokkaisho 62-288002, Tokkaisho 63-267667, Tokkaihei 2-276691 and Tokkouhei 5-41991.
In the above-described sheet finisher, sheets having an image formed on them conveyed out from the image forming apparatus mainframe are gripped and conveyed by a pair of conveyance rollers, and are successively stacked in an intermediate stacker while being collated, to be received as a bunch of sheets for one volume, and then they are subjected to an finish-processing by a stapler etc.; thus, the bunch of sheets subjected to the binding processing is then placed on an ejection belt provided at the bottom of the above-described intermediate stacker to be conveyed, and further it is gripped between an upper-and-lower pair of ejection rollers and ejected onto an output tray.
In Tokkaihei 9-235069, it is disclosed. to efficiently carry out the conveyance of sheets without stopping the sheet finisher during the interval for the transfer of operation from the finish-processing of the preceding bunch of sheets to the conveyance of the succeeding bunch of sheets, using a small-sized sheet finisher comprising a first sheet entry path for guiding a sheet conveyed out of an image forming apparatus, a second sheet entry path which diverges from said first sheet entry path at the upstream side and joins it at the downstream side, and a sheet conveyance means which makes the leading edge portions of the two sheets which have been conveyed through said first sheet entry path and second sheet entry path respectively get engaged with a conveyance roller pair to grip them in the overlapped state and then feeds them to the above-described intermediate stacker, wherein the first one of the succeeding sheets coming through the first sheet entry path is stopped by being engaged with the conveyance roller pair in still standing, the second sheet coming through the second sheet entry path is stopped to be on standby by being engaged with said conveyance roller pair in still standing in the state of being overlapped on the first sheet, and after the preceding bunch of sheets bound by a stapler is ejected from said intermediate stacker, the first one and the second one of the succeeding bunch of sheets are fed into said intermediate stacker at the same time as they are overlapped.
In order to convey two thick sheets in the state of being overlapped at the same time by a pair of conveyance rollers, a large conveying pressure is required, which makes the driving source large-sized too. If the initial sheet is conveyed out by this large conveying pressure and is made to strike against the outer circumferential surface of a conveyance roller located downstream, it produces problems such as roller contamination and the shortening of the roller life.
If the conveying pressure of the conveyance rollers is controlled to be varied, or a conveyance path is separately provided, the sheet finisher is made complex.
When the leading edge portions of the sheets conveyed by a conveyance means is made to strike against a stopper for truing up the leading edges and then the sheets are ejected into the above-described intermediate stacker, in order to improve the conveyance performance of the sheets, a wave-shaped deformation is formed in the direction parallel to the sheet conveying direction by conveyance rollers composed of a driving roller unit and a follower roller unit.
FIG. 17 shows a pair of conveyance rollers in a conventional sheet finisher; FIG. 17(a) shows the front view, and FIG. 17(b) shows the side cross-sectional view.
The rotary shaft RO of the aforesaid driving roller unit at the entrance of the intermediate stacker is supported in a manner capable of rotating by the apparatus mainframe, is connected to the driving source, and rotates for driving. To the rotary shaft R0, the driving roller members R1 having a circumferential surface made of an elastic rubber, and flange rollers R2 having an outer diameter larger than the outer diameter of the driving roller members R1 made of a hard material are fixed.
The flange rollers R2 carry it out to true up the leading edge portion of the sheets having been conveyed by the conveyance means by stopping them, and form a wave-shaped deformation in the sheets.
The follower rollers (pinch rollers) R3 of the follower roller unit are urged by the roller pressing springs sp, to make pressing contact with the driving roller members R1.
When a thick sheet is conveyed by the driving roller members R1 and the follower rollers R3 in the state of pressing contact with them, the urging spring force by the roller pressing springs sp must be set to a strong level. However, if a thin sheet is conveyed by this strong urging spring force, the sheet P is damaged.
It is an object of this invention to improve the conveying capability for a thick sheet without damaging a thin sheet.
In the case where sheets ejected from an image forming apparatus are brought in a conveyance path of the conveyance means of a sheet finisher and conveyed by conveyance rollers, during the bind-processing of the preceding bunch of sheets, if two sheets composed of the first one and the second one of the succeeding sheets are conveyed by conveyance rollers at the same time as the two sheets are overlapped, the waiting time for the bind-processing is shortened, which improves the processing speed.
However, if the conveyance of two sheets being overlapped is carried out, the truing-up performance of the sheets by the aligning operation will become worse because the two sheets are made in close contact with each other by the static electricity etc. Further, when the side edges of thick sheets in the width direction is trued up by the aligning plates of the aligning means, if the side edges of the thick sheets in the width direction are strongly pressed by the aligning plates, the stepping motor for driving the aligning plates goes out of tuning by the resisting force of the thick sheets, which lowers the sheet truing-up performance after that.
In a conventional sheet finisher, driving of the stapler has been done at the same measured timer value for a thick sheet and a thin sheet through measuring the passing of the trailing edge by a sheet passage sensor. However, for thick sheets having different conveyance characteristics from a usual sheet, dispersion in the sheet passage time from the sheet passage detecting sensor to the conveyance rollers at the entrance of the intermediate stacker is produced depending on the kinds of sheet.
Especially, with respect to sheets having a smooth surface and a high stiffness, the above-described sheet conveyance time becomes greatly prolonged, and the leading edge portion in the progressing direction of the last sheet can not reach the stopper near the stapler in the sheet conveying direction before the start of the bind-processing, to produce a deviation of the leading edge portion of the last sheet in the progressing direction.
In order to solve the above-described problems in the case of conveying thick sheets, if a uniformly prolonged sheet passage time in the sheet finisher FS is set, in the case of the conveyance of usual sheets, it cannot follow the sheet conveyance speed in the image forming apparatus, and the productivity of the processing in the image forming apparatus is lowered.
Accordingly, to overcome the abovementioned problems, a sheet conveyance apparatus and a sheet finisher, embodied in the present invention, will be described as follow:
(1) A sheet conveyance apparatus, comprising: a sheet conveyance path along which a sheet is conveyed; a first conveyance means for gripping and conveying said sheet along said sheet conveyance path; a gripping pressure change means for changing a gripping pressure of said first conveyance means; and a controller to control said gripping pressure change means in response to a thickness of said sheet gripped and conveyed by said first conveyance means.
(2) A sheet finisher, comprising: a conveyance means for conveying a sheet in a sheet conveying direction; an intermediate stacker to stack said sheet conveyed by said conveyance means; an aligning device to align sheets stacked on said intermediate stacker by pressing them in a direction perpendicular to said sheet conveying direction; a binder to bind a bunch of said sheets stacked and aligned on said intermediate stacker; an ejecting means for conveying and ejecting a bunch of said sheets bound by said binder; a drive means for driving said aligning device; a controller to control said drive means; and an overlapped sheets conveyance means for gripping and conveying two sheets, in which a succeeding sheet overlaps a previously conveyed sheet, so as to store them in said intermediate stacker, wherein said controller controls said drive means in a manner such that said aligning device aligns an initial one sheet stacked on said intermediate stacker under a first aligning condition, while said aligning device aligns two overlapped sheets, which are stacked on said intermediate stacker, under a second aligning condition.
(3) A sheet finisher, comprising: a conveyance means for conveying a sheet ejected from an image forming apparatus; an intermediate stacker to stack said sheet conveyed by said conveyance means; a binder to bind a bunch of said sheets stacked on said intermediate stacker; an ejecting means for conveying and ejecting a bunch of said sheets bound by said binder; a drive means for driving said conveyance means; a controller to controll said drive means; and a detector for detecting an end of said sheet passing through said conveyance means, wherein said controller controls said binder in a manner such that said binder binds a bunch of said sheets after a first predetermined time has passed since said detector detected an end of a final sheet included in a bunch of said sheets, serving as one file, while, when said controller determines that said conveyance means conveys thick sheets, said binder binds a bunch of said thick sheets after a second predetermined time, set by extending said first predetermined time, has passed since said detector detected an end of a final thick sheet included in a bunch of said thick sheets.
Further, to overcome the abovementioned problems, other sheet finisher and image forming apparatus, embodied in the present invention, will be described as follow:
(4) A sheet finisher, comprising: conveyance means for conveying sheets ejected from an image forming apparatus, an intermediate stacker for receiving a stack of the sheets conveyed by said conveyance means, binding means for carrying out bind-processing for a bunch of said stacked sheets received in said intermediate stacker, ejecting means for ejecting the bunch of sheets having been subjected to the bind-processing, drive means for driving said conveyance means, and control means for controlling the driving of said drive means, wherein said conveyance means comprises a second conveyance roller means for feeding the sheets in said intermediate stacker, a first conveyance roller means disposed at the upstream side of said second conveyance roller means in the conveying direction for conveying the sheets to said second conveyance roller means as gripping them in between, and a sheet guiding path for guiding the sheets conveyed from said first conveyance roller means to said second conveyance roller means, said first conveyance roller means is equipped with a gripping pressure change means for making it possible to change the gripping-pressing force of said first conveyance roller means, and said control means carries out a control so as to make it possible to convey a plurality of sheets overlapped on one another at the same time by said first conveyance roller means and said second conveyance roller means and change the gripping-pressing force for the sheets conveyed by said first conveyance roller means.
(5) A sheet finisher, comprising: conveyance means for conveying sheets ejected from an image forming apparatus an intermediate stacker for receiving a stack of the sheets conveyed by said conveyance means, binding means for carrying out bind-processing for a bunch of said stacked sheets received in said intermediate stacker, ejecting means for ejecting the bunch of sheets having been subjected to the bind-processing, drive means for driving said-conveyance means, and control means for controlling the driving of said drive means, wherein said conveyance means comprises a second conveyance roller means for feeding the sheets in said intermediate stacker, a first conveyance roller means disposed at the upstream side of said second conveyance roller means in the conveying direction for conveying the sheets to said second conveyance roller means as gripping them in between, and a sheet guiding path for guiding the sheets conveyed from said first conveyance roller means to said second conveyance roller means, and said control means carries out a control so as to make it possible to convey a plurality of sheets overlapped on one another at the same time by said first conveyance roller means and said second conveyance roller means and prohibit the conveyance of two sheets being overlapped in the case where it is set to the thick sheet.
(6) A sheet finisher, which conveys sheets ejected from an image forming apparatus by a conveyance means, receives a stack of the sheets in an intermediate stacker, carries out bind-processing by a binding means, and then ejects the sheets by an ejecting means, wherein said conveyance means comprises a first conveyance roller means for conveying the sheets as gripping them in between, a second conveyance roller means disposed at the downstream side of said first conveyance roller means in the conveying direction for conveying the sheets to said intermediate stacker, a pair of guide members facing to each other which form a sheet conveyance path between said first conveyance roller means and said second conveyance roller means, a guiding portion provided in said guide members in a projecting manner so as to make a part of said sheet conveyance path form a path having a minimum spacing capable of letting the sheets pass through, and a pressing-contact releasing means for releasing the pressing contact of the follower roller which is pressed to get contact with the driving roller of said first conveyance roller means, and when said pressing-contact releasing means releases the pressing contact of the follower roller which is pressed to get contact with the driving roller of said first conveyance roller means, the guiding portion provided in said guide members presses the sheets to the follower roller side, to make the sheet conveyance possible.
(7) A sheet finisher comprising: conveyance means for conveying sheets ejected from an image forming apparatus conveyance roller means composed of a drive conveyance roller and a driven conveyance roller for ejecting the sheets conveyed by said conveyance means onto an intermediate stacker after stopping the sheets for truing up the leading edges, and binding means for carrying out bind-processing for a bunch of sheets stacked in said intermediate stacker, said drive conveyance roller being composed of a rotary shaft connected to a drive source, driving roller members which are fixed to said rotary shaft and are pressed to the follower roller members of said driven conveyance roller, a hard flange members which are fixed to said rotary shaft and located close to one side of said driving roller members in the direction of the rotary shaft respectively, and elastic flange members which are fixed to said rotary shaft and located close to the other side of said driving roller members in the direction of the rotary shaft respectively, said sheet finisher conveying the sheets by the rotation of said drive conveyance roller and said driven conveyance roller as gripping them between the rollers, forming a wave-shaped deformation parallel to the conveying direction in the sheets.
(8) An image forming apparatus, which is equipped with a sheet finisher set forth in any one of the above-described paragraphs (4) to (7).
(9) A sheet finisher, comprising: a conveyance roller means for conveying sheets, wherein said conveyance roller means comprises conveyance rollers and a gripping pressure change means for changing the pressing force of said conveyance rollers for gripping the sheets in between, and said gripping pressure change means comprises a plate spring, an oscillation driving member, oscillation receiving member, and a solenoid, and makes the pressing force of said conveyance rollers able to be changed in accordance with the thickness of the sheets recognized by a recognizing means for recognizing the thickness of the sheets.
(10) A sheet finisher, comprising: conveyance means for conveying sheets, an intermediate stacker for stacking the sheets conveyed, aligning means for aligning the sheets stacked on said intermediate stacker by pressing them in the direction perpendicular to the sheet conveying direction, binding means for carrying out bind-processing for a bunch of the sheets stacked on said intermediate stacker and aligned by it, ejecting means for conveying and ejecting the bunch of sheets having been subjected to the bind-processing, drive means for driving said aligning means, and control means for controlling said drive means, where in said control means controls said drive means for driving said aligning means in a manner such that the alignment of the sheets is carried out, in the first alignment condition in the case where the alignment is made for a predetermined number of sheets (or less) stacked on said intermediate stacker, and in the third alignment condition in the case where the alignment is made for a number of sheets exceeding the predetermined number.
(11) An image forming apparatus, equipped with the sheet finisher set forth in the above-described paragraph (10).